It is generally known to use a device to evaporate a volatile material into a space, particularly a domestic space, in order to deliver a variety of benefits, such as air freshening or perfuming of the air. Non-energized systems, for example, systems that are not powered by electrical energy, are a popular way for the delivery of volatile materials into the atmosphere. These systems can be classified into those that require human actuation, such as aerosols, and those which do not required human actuation, such as wick based systems and gels. The first type delivers the volatile materials on demand and the second type in a more continuous manner.
One type of apparatus for delivering a volatile material is disclosed in U.S. Pat. No. 4,161,283. It discloses an article for delivering a volatile material comprising a reservoir, polymeric sheet or membrane, and a barrier layer releasably bonded to the outer wall of the reservoir. One drawback with this type of article is its susceptibility to de-lamination and leakage because the volatile materials are in contact with the membrane during storage or non-use. Another drawback may be that volatile materials build up in the membrane during storage, resulting in a spike in intensity immediately after the barrier layer is removed. Another drawback may be that the peel force makes it is difficult to remove the barrier layer without damaging the polymeric sheet or membrane. Yet another drawback may be the selectivity of the membrane in that it does not easily allow low vapor pressure volatile materials to diffuse through the polymer.
Another apparatus for delivering a volatile material is disclosed in U.S. Pat. No. 4,824,707. It discloses a decorative air freshener unit having a capsule containing a supply of volatile fragrance. The capsule is trapped between a microporous sheet and a backing sheet. The capsule is ruptured by applied force and the released fragrance is absorbed into the microporous sheet which gradually exudes the fragrance. This approach may limit the longevity of a scent since liquid is released all at once to the microporous sheet, and there is little control over the manner in which the liquid will wet the microporous sheet.
As such, there exists a need for an apparatus for delivering, over a period of time, a consistent release of volatile materials having a broad range of molecular weights and vapor pressures.